1. Field of the Invention
This invention relates to the field of automated packaging systems. Specifically, the present invention relates to carrier tape packaging systems utilizing pressure sensitive adhesive (PSA) tape. More particularly, the present invention refers to the usage of multiple and split PSA tape stratums for a carrier tape packaging system.
2. Description of the Prior Art
The present invention relates to a carrier tape packaging system for small components utilizing pressure sensitive adhesive (PSA) tape stratums.
Small components such as integrated circuit (IC) devices, are particularly susceptible to damage by mechanical forces and by electro-static discharge. Mechanical stress to the surface of the IC can cause structural damage to internal locations at points within the IC which are particularly susceptible to physical distortion. Therefore, it would be a significant advantage if small components such as ICs could be packaged and removed from the package in a manner which reduces the mechanical stress applied to the IC and, simultaneously, eliminates the source of much electro-static charge buildup during automatic handling.
Carrier tape packaging systems are known in the prior art. Existing carrier tape packaging systems typically comprise an elongated, double sided and flexible carrier tape made of paper or plastic with a multiplicity of punched cavities utilized for retaining small electronic components, typically surface mount devices known as SMDs. Generally, heat sealed cover tapes, one on each side of the punched carrier tape, are used to retain components within the cavities.
Another existing system for retaining small components within the carrier tape is to use an embossed plastic carrier, a.k.a. blister tape. Small tub-like cavities are thermoformed into a strip of plastic. Small components are placed into the cavities, and the cavities are covered with a heat sealed cover tape. The heat sealed cover tape encloses the cavities which contain the small components. Carrier tapes which include these thermoformed cavities are known as embossed carrier tapes or blister tapes.
The inherent characteristics of both punched and embossed conventional carrier tapes provide that the small components are loose in the punched or embossed cavity. While they are retained within the recess of the cavity, the small components can move in all directions (x, y and theta). When the top cover tape is removed by peel back, vibrations are induced which can cause the small components to move out of their required orientation or jump out of the cavity. In addition, very small components can and will adhere to the cover tape because of static electric charge buildups generated during cover tape peel back and thereby not be available for automatic retrieval from their pockets. In addition, these static electric charges, however slight, can damage or destroy active electronic components through electro-static discharge (ESD).
A classic problem with conventional carrier tapes is that the peel-back of cover tape creates adverse vibrations on the carrier tape. These vibrations are particularly troublesome with extremely small, lightweight components, the position of which can be disturbed by these vibrations. Another problem is that it is impossible to heat seal the carrier tapes with total uniformity. This irregular seal causes `spikes` during peel back which result in vibration and component disorientation. Force vibrations of as little as 0.05 newton have been known to cause components to jump out of their cavities or assume positions whereby retrieval using vacuum probe nozzles is not possible. In addition, when the cover tape is peeled back, it is possible that the small component could be vibrated or pulled out of the aperture or out of its orientation. Still another problem with the cover tape is that static charges can build up on the cover tape and during the peel back they can be released as a sudden flood of charges applied to an individual small active component or to several of the small components which are highly susceptible to electrostatic discharge. Electrostatic discharge applied to small components such as integrated circuits can cause reliability concerns and catastrophic failure.
Another existing means for housing the small components is to use a punched paper carrier tape, as opposed to a plastic, both used in conjunction with top and bottom cover tapes. In addition to the problems discussed above resulting from the usage of cover tape, the paper carrier tape creates problems due to dust and paper particles which are generated when the cover tape is pulled off the carrier tape surface. In addition, the paper carrier tape can delaminate when the top cover tape is pulled off, resulting in sudden separation of a length of cover tape from the carrier with subsequent component spillage.
In another existing system, the carrier tape has a multiplicity of apertures and has a single length of pressure sensitive tape at the bottom and no cover tape. Small components are individually placed into the aperture of the carrier tape on the adhesive. When the components are removed from the adhesive surface, a vacuum tip is usually employed to remove and carry the component. Excessive adhesive strength in the component to adhesive bond can make separation of the component from the adhesive surface difficult. A poke-up needle is sometimes used to release the component from the adhesive in coordination with the action of the vacuum tip. It is often awkward to use the poke-up needles to release the small components because components and they sometimes exert unbalanced mechanical force to the small component as they push through the adhesive bottom. In addition, adhesive may adhere to the IC or other small component after it is removed from the carrier tape and the adhered adhesive causes problems when the component is placed on a printed circuit board or other mounting surface. Finally, with a film backing of pressure sensitive tape to contend with, a poke-up needle encounters considerable resistance as it tries to penetrate the adhesive and push the IC or other small component out of the carrier tape. Fine pointed needles are required to penetrate the film backing of the pressure sensitive tape; these fine points expose components to physical damage, and frequently break during repeated use, resulting in production downtime and increased probability of adhesive retention on the component.
Instead of using an aperture with a closed bottom surface, the present invention uses at least two split PSA tape stratums, instead of one, on the bottom side o the embossed carrier tape. Adjusting the gap between the two PSA tape stratums provides precise adjustment of the firmness of the adhesion between the small component and the two PSA tape stratums. The usage of multiple PSA tape stratums in small component carrier tape packaging systems provides two major advantages. First, it provides a fine adjustment of the amount of adhesive exposed to the component to achieve adhesive bond and second, it provides clearance for the poke-up needles if poke-up needles are utilized.
In many existing automated handling processes, carrier tape packaging systems are used for retaining a multiplicity of small, light and fragile electronic, mechanical or other types of components, such as integrated circuit (IC) chips. A carrier tape packaging system typically comprises an elongated, double sided and flexible carrier tape having a thickness at least equal to and preferably greater than the thickness of the small components. The elongated carrier tape comprises a multiplicity of apertures along its length for accommodating a multiplicity of small, light and fragile components. An elongated flexible thin PSA tape stratum is adhered to one side of the double sided carrier tape, such that each one of the multiplicity of apertures of the embossed carrier tape has a closed adhesive bottom constituted by a portion of the elongated PSA tape stratum. Therefore each of the multiplicity of small components can be securely retained within one of the multiplicity of apertures respectively.
A small component is subsequently released from its aperture and adhesive surface for further assembly. To remove the small components from the adhesive surface of the aperture, a vacuum tip is usually employed to remove and carry the component. Excessive adhesive strength in the component to adhesive surface bond makes separation of the component from the adhesive surface difficult and the separation is often physically stressful to the small component. Residue adhesive on the component creates further problems when the component is placed on a printed circuit board.
One common method of releasing the multiplicity of small components from the elongated carrier tape is touse reciprocating or "poke-up" needles. To remove a small component from the elongated carrier tape, a poke-up needle is positioned underneath the PSA tape stratum and aligned with the aperture containing the small component. The poke-up needle action is performed synchronously with the action of the vacuum tip. While the vacuum tip is in intimate contact with the surface of the small component, the upward movement of the poke-up needle can force the small component away from the PSA tape stratum and into the exclusive possession of the vacuum tip for carrying to subsequent assembly processing.
One problem with the conventional carrier tape having PSA tape over the bottom of the carrier aperture is that it is not very effective to use the poke needles to release the small components because the poke-up needles cannot directly engage with the small components. Instead of directly engaging, the poke-up needles poke through the PSA tape stratum, and the strength of the PSA tape stratum somewhat negates the poke-up forces. This awkward set of forces on the small component can have consequences which disrupt the normal flow of manufacturing. Unless a wide range of pressure sensitive tapes with varied adhesive characteristics is employed, it is impossible to adjust the adhesiveness of the PSA tape stratum to be strong enough to hold the small components securely, yet not excessively which would make removal of the small components difficult. The absence of control over the forces needed to remove the small component from the PSA tape stratum contribute to the overall stress which is imposed on the small component and often result in failure to retrieve components from the tape for automatic placement--a condition which seriously reduces machine throughputs and increases need for assembly rework.
The novel feature of the present invention is to use two split PSA tape stratums, instead of one, on the bottom side of the embossed carrier tape. A very precise gap is maintained between the two split PSA stratums along the centers of the multiplicity of apertures of the carrier tape. This very precise gap serves two purposes: first, it provides an accurate means for adjusting how firmly the small components are attached to the PSA tape stratum, and second, it provides a clearance for the poke-up needles to directly engage the small components.
When a small component is retained within an aperture, it is adhered to the two split PSA tape stratums. A portion of the bottom surface of the small components is not adhered to either PSA tape stratums because of the gap between the two PSA tape stratums. Adjusting the gap between the two PSA tape stratums provides precise adjustment of the firmness of the adhesion between the small component and the two PSA tape stratums.
Multiple PSA tape stratums provide the capability of a micrometer-like adjustment of the adhesive strength of the small component to PSA tape bond. In varying the surface area exposed to the small component by adjusting the gap width between the two tapes, removal of the small component is thereby made more controlled with improved reliability in automated component retrieval and placement. By adjusting the gap distance of the tape, the surface area of the tape overlying the small component is thereby controlled, resulting in a micrometer-like adjustment of the adhesive suitable for high speed automated processing.
The adhesive strength of the tape-to-component bond is constrained by two extremes. The adhesive strength should be at least as great as that which is required to hold the small component in place securely while the component is moving during processing and the adhesive strength should be less than that which could impede or prevent removal of the small component during high speed automated processing.
Another significant benefit of utilizing multiple PSA tape stratums in conjunction with carrier tape, is that the gap region spacing between the PSA tapes provide clearance for the poke-up needles, when the poke-up needles are used to assist removal of the small component, thereby avoiding: the force needed by the poke-up needle to protrude through a solid PSA tape bottom; and the possibility of the retention of any adhesive on the removed component. The clearance for the poke-up needle, provided by the two PSA tapes, will be present even if the gap between the two tapes is set to zero. It is particularly significant that a blunt or flat pointed poke-up needle may be employed because of gap spacing between the PSA tapes. When a heretofore single strand of PSA tape has been utilized, the point of the poke-up needle must be sharp in order to penetrate the film backing of the PSA tape. Sharp points on poke-up needles break off frequently during usage, resulting in production downtime for replacement and increased probability of transfer of adhesive residue to components when broken point poke-up needles are unnoticed and not replaced.
The following twelve patents are the closest prior art of which the inventor is aware.
1. U.S. Pat. No. 3,881,245 issued to Dudley et al. (hereafter the "Dudley Patent") on May 6, 1975 for "Mounting Electrical Components on Thick Film Printed Circuit Elements".
2. U.S. Pat. No. 4,575,995 issued to Tabuchi et al. (hereafter the "Tabuchi Patent") on Mar. 18, 1986 for "Automatic Producing Apparatus of Chip-Form Electronic Parts Aggregate".
3. U.S. Pat. No. 2,885,849 issued to Wohlman, Jr. (hereafter the "Wohlman Patent") on May 12, 1959 for "Semiconductor Taping Apparatus".
4. U.S. Pat. No. 3,177,629 issued to Anspach (hereafter the "Anspach Patent") on Apr. 13, 1965 for "Apparatus for Loading Components".
5. U.S. Pat. No. 4,340,774 issued to Nilsson et al. (hereafter the "Nilsson Patent") on Jul. 20, 1982 for "Device for Mounting Circuit Components on a Circuit Board".
6. U.S. Pat. No. 3,691,436 issued to Maijers et al. (hereafter the "Maijers Patent") on Sept. 12, 1972 for "Electrical Circuit Element having a Diagonal Abutment Strip and Method of Manufacturing the Same".
7. U.S. Pat. No. 3,971,193 issued to Tardiff et al. (hereafter the "Tardiff Patent") on Jul. 27, 1976 for "Machines for Sequencing Diverse Components".
8. U.S. Pat. No. 4,724,954 issued to Sillner (hereafter the "Sillner Patent") on Feb. 16, 1988 for "System for Conveying and Guiding Components, in Particular Electrical Construction Elements Which are Held on a Belt in a Radially or Quasi-Radially Belted Manner".
9. U.S. Pat. No. 4,954,207 issued Higuchi et al. (hereafter the "Higuchi Patent") on Sep. 4, 1990 for "Apparatus for Automatically Taping Electronic Components".
10. U.S. Pat. No. 3,608,711 issued to Wiesler et al. (hereafter the "First Wiesler Patent") on Sept. 28, 1971 for "Package for Electronic Devices and the Like".
11. U.S. Pat. No. 3,785,507 issued to Wiesler et al. (hereafter the "Second Wiesler Patent") on Sept. 28, 1971 for "Die Sorting System".
12. U.S. Pat. No. 4,298,120 issued to Kaneko (hereafter the "Kaneko Patent") on Nov. 3, 1981 for "Chip-Like Electronic Component Series and Method for Supplying Chip-Like Electronic Components".
The first wiesler patent discloses a package for electronic devices and the like, which utilizes a tape 12 with a plurality of openings 14 in the tape 12 to receive a device 10. The device 10 is held in place by an adhesive tape, applied from the back, which is exposed at the opening and serves as a tape stratum 16 for holding the device 10 in place.
In contrast, the present invention is a combination of a carrier tape with apertures, used with a double PSA tape, set onto the underneath surface of the carrier tape, so that the device can be placed onto the two surfaces of tape. The gap between the two surfaces of tape can be set with a micrometer type accuracy so the device can be easily extracted from this arrangement. The gap provides a clearance for the poke-up needle which pushes the device out of the tape arrangement so it may be handled by the vacuum tip of a pick and place machine.
The Tabuchi patent discloses an automatic producing apparatus of chip-form electronic parts aggregate. In FIG. 4 of the Tabuchi patent, there is a tape-like housing body formed by the automatic producing apparatus of the Tabuchi disclosure. The tape-like housing body has a feed hole along the side and a frame type housing hole with a specific pitch between the housing holes.
In the Tabuchi patent, there is once again a tape covering which essentially covers the entire portion of the carrying tape which thereby introduces all of the problems that have been addressed in the prior art. In the present invention this is overcome by a set of two tapes which have variably set gap distances to facilitate efficient retention of the small components and adjustable adhesive strength of the tapes. In utilizing the multiple PSA tape stratums, the small components are affixed in such a way that provides clearance for the poke-up needles so the small component can be easily removed and by permitting the gap width between the tapes to be adjustable, the strength of the tape to component bond can, in such a manner, be finely controlled.
The second Wiesler patent discloses a die sorting system which uses a strip 140 comprised of a relatively narrow strip formed with indexing holes 142 along one edge, and storage holes 144 near the outer edge of the strip. On the bottom side, a thin pressure sensitive adhesive tape 146 is laminated to the strip 140 and provides an adhesive floor, to hold the die 100, at the bottom of the storage holes.
The Kaneko patent discloses a chip-like electronic component series and method for supplying chip-like electronic components, comprising a tape-like member formed with a plurality of apertures with upper and lower cover sheets that contain small chip-like electronic components. FIGS. 19 and 20 illustrate the upper tape 72 and lower tape 74 relation to the receiving concavity 70.
The Anspach patent discloses an apparatus for loading components. These components are primarily larger components than what the present invention envisions and are primarily leaded diodes. The present invention is intended for use primarily with leadless electronic components or surface-mounted devices (SMDs). Referring to FIG. 5, there is a gap in the carrier where the heads of the transistors are placed but the transistors themselves are carried by having the lead sandwiched between the carrier tape and an adhesive tape.
The Higuchi patent discloses an apparatus for automatically taping electronic components. The electronic pitch and an adhesive tape is applied to fix the electronic components in position. One of the main points of the Higuchi patent is that the electronic component is placed on an elongated first tape and by applying a second tape, the component is fixed between the two tapes.
The Dudley patent discloses a device for mounting electrical components on thick film printed circuit elements. Two metal strips 15 and 16 are attached to printed areas 14, adhered by electrical resistance welding for contacting electrodes.
The Wohlman patent discloses a semiconductor taping apparatus. The semiconductors are taped at lateral ends by a pair of tapes 73, and another pair of tapes 74 where the adhesives in tapes 73 face the adhesive side of the tapes in the second pair of tapes 74.
The Nilsson patent discloses a device for mounting circuit components on a circuit board which include apertures in the plate designed to hold by means of a friction fit.
The Maijers patent discloses an electrical circuit element having a diagonal abutment strip and method of manufacturing the same. In the Maijers patent, small discrete components are interconnected by means of a strip of tape.
The Tardiff patent discloses machines for sequencing diverse components. In the Tardiff patent, small electrical components are sequenced and interconnected with tape at opposite ends of their lead portions.
The Sillner patent discloses a system for conveying and guiding components, in particular electrical construction elements which are held on a belt in a radially or quasi radially belted manner. The components in the Sillner patent are also held by tape at the ends of their leads.
Therefore, none of the prior art have combined the concept of having an invention which utilizes multiple PSA tape stratums as an integral part of a small component packaging system, which: provides a micrometer-like adjustment of the adhesive strength of the small component to PSA tape by adjusting the gap width between the tapes, facilitating removal and further processing; and provides a clearance so the poke-up needles can push up through the gap of the tapes, thereby assisting in the removal of the small component from the carrier tape and PSA tape arrangement.